That would mean a member of this board went and told them.
More likely they drop a bunch of articles that they know have been indexed in Google every so often and do a simple search.
This kinda thing really bugs me because as long as they get a dofollow link it's a no-brainer for them.
People like me hear about a publication they have never heard of and may then click through and subscribe to. And they build backlinks that help their SEO.
There is nothing either good or bad, but thinking makes it so.